The invention relates to a screw conveyor arrangement particularly adaptable for use in a combine harvester and more particularly, for conveying and elevating clean grain from a cleaning shoe to a grain tank above the shoe.
For convenience, the present invention will be discussed with reference to the requirements for clean grain handling in a combine although it is adaptable to any screw conveyor system involving a change of conveying direction from generally horizontal in one direction to generally upward, with the total change of direction being more than ninety degrees.
The most common combine clean grain handling arrangement, especially for larger combines, involves three conveyor legs: a lower transverse conveyor beneath the cleaning shoe for collecting and conveying clean grain to one side of the combine; a generally upright conveyor to elevate the clean grain to the level of the grain tank; and a third conveyor leg for conveying the grain laterally and delivering it to a central portion of the grain tank. However, U.S. Pat. No. 4,067,343 Muijs, discloses an arrangement in which the upright conveyor leg is inclined inward so that it delivers material close to the center of the grain tank thus eliminating the need for an upper lateral conveyor. Screw conveyors are used, but the upright conveyor is offset from the transverse bottom conveyor, requiring a relatively complex and costly transfer housing and drive arrangement at the junction of the two portions of the conveyor.
British Pat. No. 852,210 Hansen discloses (but only in the context of a grain wagon) a simplified screw conveyor arrangement for changing direction from a horizontal to an upright portion. The axes of both screw conveyor portions lie in a common plane and, at their junction, their shafts are drivably connected through a pair of bevel gears external to the passages through which grain is conveyed. However, the change of direction between the two conveyor portions is limited to ninety degrees and transfer from one conveyor portion to the other, is somewhat indirect and relies, at least in part, on deflecting surfaces within a transfer housing, friction of grain on these surfaces results in relatively high power consumption as well as increased possibility for grain damage.